# TIP 202: Add 2>@1 Special Case to [open] and [exec]
Author: Jeff Hobbs <[email protected]>
State: Final
Type: Project
Tcl-Version: 8.5
Vote: Done
Created: 19-May-2004
Post-History:
Keywords: Tcl, redirection
Tcl-Ticket: 957132
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# Abstract
This TIP proposes adding a new redirection case '2>@1' that redirects
the error channel to the output channel in **open** and **exec**.
This would only be valid at the end of a pipeline.
# Rationale
Tcl is currently limited on how _stderr_ can be managed from a
command opened with **open \|** or **exec**. This TIP adds the
ability to simply combine the _stderr_ stream with the _stdout_
stream by adding a new output redirection case, **2>@1** \(i.e. as in
Bourne shell syntax\), that is only ever valid as the last redirection
item in a pipeline. This will enable simple capturing of _stderr_
as well as _stdout_ across platforms.
The behavior is similar to **2>@stdout**, but that does not work
across platforms. The difference is that directs to a real _stdout_
file channel \(which is not available in Windows wish for example\),
whereas **2>@1** would redirect to the output result for
**exec**/**open**.
The intention is to handle the common case of wanting to capture
_stderr_ as well as _stdout_ output from a single command. This
operator is only valid as the last redirection operator. To redirect
_stderr_ of previous commands along with their _stdout_, use the
preexisting **\|&** pipe operator.
This is backwards compatible as **2>@1** currently raises an error
that "1" is not a valid file id \(Tcl does not create such file ids\).
## Examples
set fid [open "|$cmd 2>@1"]
set result [exec $cmd 2>@1]
# Reference Implementation
See SF Tcl Patch 957132
<http://sf.net/tracker/?func=detail&aid=957132&group_id=10894&atid=310894>
for details.
# Copyright
This document has been placed in the public domain.